Inferring the dark matter splashback radius from cluster gas and observable profiles in the FLAMINGO simulations

Monthly Notices of the Royal Astronomical Society, vol. 529, pp. 2017–2031

Abstract

ABSTRACT The splashback radius, coinciding with the minimum in the dark matter radial density gradient, is thought to be a universal definition of the edge of a dark matter halo. Observational methods to detect it have traced the dark matter using weak gravitational lensing or galaxy number counts. Recent attempts have also claimed the detection of a similar feature in Sunyaev–Zel’dovich (SZ) observations of the hot intracluster gas. Here, we use the FLAMINGO simulations to investigate whether an extremum gradient in a similar position to the splashback radius is predicted to occur in the cluster gas profiles. We find that the minimum in the gradient of the stacked 3D gas density and pressure profiles, and the maximum in the gradient of the entropy profile, broadly align with the splashback feature though there are significant differences. While the dark matter splashback radius varies with specific mass accretion rate, in agreement with previous work, the radial position of the deepest minimum in the log-slope of the gas density is more sensitive to halo mass. In addition, we show that a similar minimum is also present in projected 2D pseudo-observable profiles: emission measure (X-ray), Compton-y (SZ), and surface mass density (weak lensing). We find that the latter traces the dark matter results reasonably well albeit the minimum occurs at a slightly smaller radius. While results for the gas profiles are largely insensitive to accretion rate and various observable proxies for dynamical state, they do depend on the strength of the feedback processes.

Authors 13

1. Imogen Towler corresponding

   University of Manchester

   Affiliation as printed

   Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester , Manchester M13 9PL , UK

2. Scott T. Kay

   University of Manchester

   Affiliation as printed

   Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester , Manchester M13 9PL , UK

3. Joop Schaye Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden , the Netherlands

4. Roi Kugel Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden , the Netherlands

5. Matthieu Schaller Aachen Leiden Observatory Lorentz Institute for Theoretical Physics

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden , the Netherlands

   Lorentz Institute for Theoretical Physics, Leiden University , PO box 9506, NL-2300 RA Leiden , the Netherlands

6. Joey Braspenning Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden , the Netherlands

7. Willem Elbers

   Durham University

   Affiliation as printed

   Institute for Computational Cosmology, Department of Physics, University of Durham , South Road, Durham DH1 3LE , UK

8. Carlos Silvestre Frenk

   Durham University

   Affiliation as printed

   Institute for Computational Cosmology, Department of Physics, University of Durham , South Road, Durham DH1 3LE , UK

9. Juliana Kwan

   University of Cambridge · Liverpool John Moores University

   Affiliation as printed

   Astrophysics Research Institute, Liverpool John Moores University , Liverpool L3 5RF , UK

   Department of Applied Mathematics and Theoretical Physics, University of Cambridge , Wilberforce Road, Cambridge CB3 0WA , UK

10. Jaime Salcido

    Liverpool John Moores University

    Affiliation as printed

    Astrophysics Research Institute, Liverpool John Moores University , Liverpool L3 5RF , UK

11. Marcel P. van Daalen Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden , the Netherlands

12. Bert Vandenbroucke Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University , PO Box 9513, NL-2300 RA Leiden , the Netherlands

13. Edoardo Altamura

    University of Manchester

    Affiliation as printed

    Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester , Manchester M13 9PL , UK